Control means



June 8, 1937.l B; w. 'JONES 2,083,531

CONTROL MEANS Filed Nov. 28, 1936' 2 sneetsfsneex 1g l Flbfl. a@ if J6 af i 352%; y Y 3i A /7 Q l. A 4417, "4a -40 40 :gli 2/ l l i 4 v l i o n o O Q ab u @D Inventor: Benjamin W dones,

by 7?/ His Attorney June 8, 1937# B, w JONES 2,083,531

CONTROL MEANS Filed Nov. `:28, 1936 Y sheets-sheer 2 Invento; Berljamin W. dones,

Patented" `lune 8, 19371 CONTR() L M 'EANS Benjamin W. Jones, Schenectady, N. Y., assignor to General Electric Company, a corporation cf New York Application November 28, 1936, Serial No. 113,167

11 Claims.

My invention relates to control'means, more particularlyI to differential control means for maintaining substantially. constant a condition to becontrolled and has for an object the provision oi simple, reliable, and inexpensive control means of this character.

In the application of electric motors, particu- `larly asynchronous alternating current motors,` to various types of machinery, for example, to

printing` press drives, it is oftendesirable to maintain a relatively low speed during certain portions of the operation. This low speed may be on the order of 10% speed and since the load may vary over wide limits, it is essential that l5 means be provided for varying the secondary or rotor resistance of the driving motor over a Wide range. t

Various control devices have heretofore been proposed for accomplishing such speed control of asynchronous alternating current motors. While some of these devices have been found relatively satisfactory, they likewise have been found objectionable from the standpoint of cost and have been subject to operating and installation diiulties.

Accordingly, it is a further o-bject of my invention toprovide simple and reliable speedcontrol `means for an induction motor arranged to maintain a substantially constant low speed.

In carrying out my invention in one form, I provide a plurality of contacts mounted for vibratory movement and a plurality of co-operating contacts normally positioned beyond and selec- 'tively movable into the range of vibration so as to provide selective intermittentengagement of the contacts. In addition, means responsive to the condition to be controlled are provided for moving the izo-operating contacts into and out of the range of vibration and means controlled by the selective engagement and disengagement of the contacts are provided for varying the condition to be controlled.

More speciiically, I provide a pair of small auxiliary motors respectively energizable from the 45 primary and secondary circuits of a wound rotor induction motor the speed of which is to be controlled, and a differential mechanism driven by these auxiliary motors is'provided for moving the cci-operating contacts into and out of the range of vibration in accordance with variations in the speed of the, induction motor. Means controlled by engagement and disengagement of the contacts are provided for varying the secondary rel sistanceof the induction motor to control its speed, the intermittent engagement of the controlling contacts preventing overshooting of this resistance controlling means.

The duration of contact engagement during each vibration of the contacts increases gradually as the coi-operating contacts are moved by the diiierential mechanism and each co-operating Contact is arranged to provide continuous engagement with its associated vibrating contact before the next co-operating contact is moved into the range of vibration. Furthermore, the cams which are operated by the differential mechanism to drive the co-operating contacts are adjustably secured to the diierential mechanism so as to provide for variation inthe sequential movement of the co-operating contacts.

For a more complete understanding of my invention, reference may now be had to the drawings in which Fig. l is a plan viewof a control device embodying my invention; Fig. 2 is an elevational view of the device shown in Fig. l; Fig. 3 is a fragmentary View of the differential mechanism with a portion of the casing removed to illustrate the internal gearing; Fig. 4' is an end view oi' the device shown in Fig. 1 with certain parts broken away; and Fig. 5 is a somewhat diagrammatic View of the control device applied to the control of an induction motor.

Referring now to the drawings, I have shown my invention as applied to a control device comprising a base plate I Il to which a U-shaped frameV I I and an insulating base member I2 are secured for respectively supporting the diierential mechanisin and the contact mechanism to be described hereinafter. Also mounted on the base plate I0 is a pair of small auxiliary motors I3 and I4 which may be any well known alternating current type of motor, the speed of which varies at constant load with the frequency of the source of alternating current supply. For e ample, the auxiliary motors are shown as fractional horse-power, single phase, shaded-pole induction motors.

As shown, the auxiliary motor I3 is mounted -on a support I5 (Fig. 2) and is connected through suitable red'uction gearing (not shown) tol a shaft I6 coupled by means ofa coupling I'I to a second shaft I8 which extends across and is. jcurnaled in the two legs ofthe U-shaped frame- II. Secured to the extending end of the shaft I8 is a gear I9 which meshes with a similar gear 20 mounted on the end of the differential shaft 2|. As shown, the gears I9 and 20 are partially enclosed by.. means of a suitable cover plate 22.

m Likewise, the motor I4 is mountedon a support 23 carried by the supporting posts 24 and is connected by suitable reduction gearing (not shown) to a shaft 25 which is connected by a coupling 26 to a differential shaft 21 journalled in one leg of the frame II.

The differential shafts 2 I, and 21 rotatably support a differential housing 28 (Fig. 3) and are provided at their innermost ends with bevel gears 29 and 38, respectively. Meshing with the bevel gears 29 and 38 and journalled on suitable stub ,shafts 3I carried by the housing 28 is a pair of bevel gears 32 and 33. As will be understood by those skilled in the art, so 'long as the gears 38 and 29 rotate at the same speed, the gears 32 and 33 rotate on their shafts 3l and the housing 28 remains stationary. Whenever a differential occurs in the speed of gears 38 and 29, however, the gears 32 and 33, together with the housing 28, rotate about the shafts 2| and 21. Normally, the differential housing 28 is biased to the position shown by a torsion spring 34.

Secured to the upper external wall of the differential housing, I provide a plurality of brackets 35 which support a plurality of annular cams 36, 31, 38, and 39. These cams surround the housing 28 and are secured thereto in predeterwhich extend through the brackets 35 and through suitable apertures 48a (Fig. 4) in the cams. As shown, each of the camsis provided with a, plurality of apertures for permitting circumferential adjustment of the cams relative to the housing. As will be more fully explained hereinafter, rotation of the differential housing 28 and the consequent movement of the cams 36 to 39, inclusive, controls the contact mechanism carried on the insulating base I2.f

This contact mechanism, as shown, comprises a tiltable frame 4I, the upper side of which carries a plurality of adjustable contacts .42, 43, 44, and 45, respectively, and the lower side of which 40 is provided with supporting legs 46. As shown best in Figs. l, 4, and 5, these legs 46 are bifurcated and engage suitable notches 41, in a pair of supporting plates 48 which-are secured to the iace of the insulating b'ase member I2, the base member I2 (Fig. 4) being provided with apertures 49 into which the bifurcated legs extend.v

Thus, the frame 4I is supported for pivotal movement on the base member I2.

Extending outwardly from the frame 4I is an arm 50, the outer end of which carries a cam follower 5I for engagingan eccentric cam 52 carried by the shaft I8. A guide post 53 which extends upwardly from the base I2 passes through a suitable aperture in the arm 58 and is provided with a spring 54, one ed of which engages a washer 55 carried by the post 53 and the other end of which engages the arm 58 so as to maintain the cam follower 5I in engagement with the periphery of the eccentric cam 52. It will be ap- I8 the eccentric cam 52 imparts to the frame 4I and to the contacts 42 to' 45, inclusive, a vibratory movement, the amplitude or .range of which is determined by the shape of the eccentric and the frequency ot which depends upon the speed of rotation o! the shaft I3.

Disposed adjacent the pivoted frame 4I, I provide a plurality of :so-operating contacts 58, 51, 53, and 59, respectively. associated with the contacts 42 w 45, inclusive, .and normally positioned of vibratory movement thereeontacts are supported l shown best inllig.4,aresecuredtointermediateportions of minedrelation to each other by the screwsv -48' parent, therefore, that upon rotation of the shaftV I 'tion ofthe operation of lower ends of which are' supported on L-shaped brackets 62 secured to the insulating base member I2, the upper ends of the resilient members 6I extending through suitable slots 63 (Figs. l and 2) formed in the rearwardly extending upper ends of the spring arms 60.- Thus, it will be seen that each of the contacts 56 to 59, inclusive, is supported for limit' movement relative to its asso' elated resilient member 6I for a purpose .to be more fully described hereinafter.-

As shown, the resilient members 6I are positioned adjacent the cams 36 to 39, inclusive, so

that upon rotation of the differential housing 28 in a counter-clockwise direction, the contacts 56 to 59, inclusive, will bevmoved toward the frame 4I and into the range of vibration of the contacts 42 to 45, inclusive, the cams 36 to 39, inclusive, being provided as shown with suitable high spots 63 to 66, respectively.

It will now be apparent that when the shaft I8 is rotated, the contacts 42 to 45, inclusive, are vibrated through a given range and that when the diiferential housing moves in a counterclockwise direction, as viewed in Fig. 5, the co-operating contacts 56 to 59, inclusive, will be sequentially moved into this range of vibration. The

high spots on the cams 36 to 39, inclusive, are so arranged that the co-operating contact 56 first moves into the range of vibration and thus an intermittent engagement and disengagement of the contacts 42 and 56 is provided,l the duration of which depends upon the distance that the contact 56 'is moved. It will be apparent that as this contact 56 moves further, the "duration of contact engagement increases, the arrangement of the spring arm 68 relative ,to the resilient support 6I being such that the cooperating contact 56 follows the contact 42 during a portion ot its vibration. l

When the contact 56 is moved to its extreme position by the high spot 63 on the cam 36, the contacts 42 and 56 remain continuously in engagement, the contact 56 following the contact 42 during its entire rarfge o! vibration. Preferably, the cams 36 and 31 are so arranged that the contact 5 6 reaches its position of continuous encontact 43 and likewise the contacts 51 and 5l are moved to their respective positions of con- ,tinuous engagement before the next succeeding contact is moved into the range of vibration.

As will be explained more fully hereinafter, the vibrating contacts 42 to 45, inclusive, and .the co-operating contacts 56 to 59, inclusive, control suitable means for varying the condition to be controlled and the contact arrangement thus far described which provides first intermittent engagement of continually increasing duration and finally continuous engagement of the contacts is highly effective in preventing chattering of the contacts and in preventing over correction in the variation of the condition to be controlled.

It is no w believed that a complete understanding of my invention may be had from a descripmy improved control device when utilized to control'the speed of an induction motor.

Referring now to Fig. 5, I have shown my improved control devicens applied to an induction motor 61, the primary winding of which is connected for energization from a suitable `source oi 3-phase alternating current represented by the conductors 6l, 69, and 1l, and the secondary circuit of which is provided with s. plurality or slip i4, l5, and lt, which sections are controlled by electromagnetic switches li, 18,1%, and tu, re'- spectively, associated therewith.

These electromagnetic switches are arranged, when operated, to short-circuit the associated resistor sections and are provided with energizing windings, the energization of which is controlled by the contacts 4i to it, inclusive, and the contacts 55 to 59, inclusive, of my improved control device in a manner to be more fully described hereinafter.

As shown, the auxiliary motor iii is connected, by means of the conductors di, for energization from the same source of alternating current supply as the primary circuit of the induction motor tl, and the auxiliary motor llt is connected across cordance with the frequency of the current in-' duced in the secondary circuit oi the induction motor.

In the drawings, the control device is shown in the position occupied when the induction motor tl is rotating at the desired low speed,`

say 10% speed, under minimum' load conditions, all of the secondary resistor sections being included in the secondary circuit of the induction motor. So long as the induction motor di continues to operate at this speed, the auxiliary motors i3 and id drive their respective diiierential gears 25 and dit at equal speeds and accordingly the differential housing tu remains in the positionrshown.

It will now be assumed that the load on the induction mtor til suddenly increases, and, as will be understood by those skilled in the art, an increase in the load on the induction motor di causes the mot'or to slow down. As the speed of the induction motor begins to decrease, however, the frequency of the current induced in its secondary circuit increases and accordingly, the

speed of the auxiliary motor i4 increases, whereupon the differential housing 28is moved in a counterclcckwise direction and the co-operating contact 5t is moved into the range of vibration of the contact 42 so as to `provide intermittent engagement therebetween. As soon as the Contact 56 engages the contact 42, an energizing circuit is established for the magnetic switch 80, which circuit may be traced from the supply conductor 'iii through the conductor 83, the frame 4|, the contacts 42 and 56, the members B0 and 6i, which support the contact 56, the conductor 84, the energizing winding of the magnetic switch 8B, and by way of the conductors 85, 86, 81, and 88 to the supply conductor 69. l

It will be apparent that energization of the electromagnetic switch 80 short-circuits the reu sistor sections 'I6 so as to decrease the resistance.

tained which decreases the resistance connected in the secondary circuit of the induction motor by an amount the average value of which depends upon the time during which the contacts 42 and 56 remain closed throughout each vibration of the contact d2. As the dierential housing 2d continues to rotate in a counterclockwise direction, the duration ci contact engagement between the contacts di and 5t increases, as described above, and accordingly the average value of the resistance `in the secondary circuit of the induction motor iii decreases so as to speed up the induction motor.

When the cO-Operating contact 56 reaches its position of continuous engagement, the electromagnetic switch tt is continuously energized so as continuously to short-circuit the resistor section it. If the removal of this amount of re- ,sistance from the secondary circuit is sumcient to increase the speed of the induction motor to the predetermined value, the speed of 'operation of the auxiliary motor i4 will be such that the differential gears tu and tu operate at equal` speeds and accordingly the movement of the difierential housing 2t will cease. if, however, the load variation on the induction motor 5l is such that the induction motor still operates at too low a speed, the differential housing 2d continues,

to rotate in a countercloclrwise direction and the co-operating contact 5i is thus moved into the range of vibration of the contact i3 intermittently to energize the electromagnetic switch 'l5 and thereby remove theresistor sections 'i5 from the secondary circuit of the induction motor.

In a like manner, if the load on the induction motor should increase suddenly to its maximum value, the differential housing 2t would continue to rotate until all of 'the associated `contacts were in their continuously closed position so as continuously to energize all of the electromagnetic switches 'il to til, inclusive, Vand thereby shortcircuit all oi the resistor sections 'i3 to l5, inclusive. It will also be apparent that if the load on the induction motor til should then decrease, the induction motor would tend to speed up and the auxiliary motor id would slow down so as to effect rotation of the differential housingytd in a clockwise direction and progressively open the associated contacts so as sequentially to insert the resistance sections i3 to' 76, inclusive, in the secondary circuit of the induction motor tl.

` In the above description, it has been assumed that the electromagnetic switches Tl to 80, inclusive, act quickly enough to follow the engagement and disengagement of the contacts controlsov ling the energizing windings thereof. Substantially the same effect may be obtained, however, when slow acting electromagnetic switches are used. Such slow acting electromagnetic switches will respond t0 the average value of current flowing in their energizing circuit, which current value is determined by the duration of contact between the contacts 42 'to 45, inclusive, and the contacts 56 to 59, inclusive. Thus, so long as the time that contact 56 engages the contact 42 during each vibration is too small to provide an average yalue of current in the energizing winding of the electromagnetic switch 80 suiicient to effect operation of this switch, none' of the resistor sections in the secondarymotor circuit are shortcircuited. Whenever the time of closure becomes great enough, however, the average current iiowingthrough thisenergizing winding will be suiicient to effect operation of the electromagnetic switch 80 and accordingly the resistor section 16 will be short-circuited. Likewise, the

remaining sections will be short-circuited when the average value of the current in the respective energizing windings becomes sumcient to operate the magnetic switches 19, 18, and 11.

As hereinbeiore mentioned, the relative positions of the cams 36 to 39, inclusive, may be adjsted by means of the screws 40 and the apertures Mia so as to vary the time sequence of operation of the contacts 56 to 59, inclusive. Furthermore, if it is desired to change the base speed which is to be maintained constant by my iml proved control device, it is necessary only'l to remove the cover plate 22 and to replace thegears i9 and 20 by similar gears having a different ratio.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. Speed control means for an electric motor,

'said speed control means comprising a plurality of contacts, means for imparting to said contacts aJvibratory movement, a plurality of cooperating contacts respectively associated with said vibratory contacts and normallypositioned beyond the range of vibration thereof, means responsive to the speed of said motor for selectively moving said cooperating contacts into and out of said range of vibration to provide selective intermittent engagement of said contacts, the duration of contact engagement during each vibration depending upon the respective positions of said cooperating contacts, said cooperating contacts at one limit of movement being positioned to provide continuous contact engagement, and means controlled bythe selective engagement and disengagement of said contacts for controlling the speed of said motor.

2. Speed control means for an electric motor, said speed control means comprising a pluralityv of contacts, means for imparting to said contacts a vibratory movement, a plurality of cooperating contacts respectively associated with said vibratory contacts and normally positioned beyond the range of vibration thereof, dinerential means responsive to variations in the speed of said motor from a predetermined speed for selectively moving said cooperating contacts into and out of said range of vibration to provide selective intermittent engagement of said' contacts, therduration of contact engagement during each vibration depending upon the respective positions of said cooperating contacts, said cooperating contacts" at one limit of movement providing continuous contact engagement, and means controlled by the selective gagement of said contacts for maintaining the speed of said motor substantially at said predetermined speed.

3. Speed control means for an electric motor,

said speed control means comprising a plural-4 engagement and` disenspeed at which said motor is operating, differential means responsive to the diiference in the speeds of said rotatable means for selectively moving said cooperating contacts into and out of said range of vibration. to provide selective intermittent engagement of said contacts, and means controlled by the selective engagement and disengagement of said contacts for varying the speed of said motor to maintain said motor speed substantially constant.

4-. Speed control means for an electric motor, said speed control means comprising a plurality of contacts, means for imparting to said contacts a vibratory movement, a plurality of cooperating contacts respectively'associated with said vibratory contacts and normally positioned beyond the'range of vibration thereof, reference means rotatable at a speed corresponding to the speed at which it is desired to operatesaid motor, means rotatable in accordance with the speed of said motor',` differential means responsive to differences in the speeds of said rotatable means for selectively moving said co-operating contacts into and out of said range of vibration in predetermined sequence to provide selective intermittent engagement' of said contacts, the duration of contact engagement during each vibration depending upon the respective positions of .said cooperating contacts, each of said cooperating contacts at one limit of movement providing continuous contact engagement, and means controlled by the selective engagement and disengagement of said-contacts for varying the speed of said motor to maintain a substantially con- -stant motor speed.

5. Speed control means for an electric motor, said speed control means comprising a plurality of contacts, means for imparting to said contacts a vibratory movement, a plurality of cooperating contacts respectively associated with said vibratory contacts and normally positioned beyond the range of vibration thereof, a pair of auxiliary motors, means energizing one of said auxiliary mo-` tors for rotation at a substantially kconstant speed, means energizing the other of said auxiliary motors for rotation'in accordance with the speed of said electric motor, differential means driven by said auxiliary motors for selectively moving said cooperating contacts into and out of said range of vibration in accordance with variations in the speed of said electric motor, whereby selective intermittent engagement of said contacts is provided, and means controlled by the selective engagement and disengagement of said contacts for vvarying the speedof said electric motor.

6. Speed control means for an electric motor, said speed control means comprising a plurality ofcontacts, means for imparting to said contacts a vibratory movement, a plurality oi cooperating contacts respectively associated with said vibratory contacts and normally positioned beyond the range of vibration thereof, a pair of auxiliary motors, means energizing one'of' said auxiliary motors for rotation at a substantially constant speed means energizing the other of said auxiliary/mo- `tors for rotation in accordance with the speed of said electric motor, differential means driven by said auxiliary motors for selectivelyfmoving said cooperating contacts into and out of said range of vibration in accordance with variations in the speed of said electric motor whereby selective intermittent engagement of said contacts is provided, the duration of contact engagement during each vibration depending upon the respective positions of said cooperating contacts, each of said cooperating contacts at one limit of movement providing continuous contact engagement, and means controlled by the selectivengagement and disengagement of said contacts for varying the speed of said electric motor.

7. Speed control means for an asynchronous motor having a primary and a secondary winding, said speed control means comprising a plurality of contacts, means for imparting a vibratory movement to tsaid contacts, a plurality of cooperating contacts respectively associated with said vibratory contacts and normally positioned beyond the range of vibration thereof, a pair of auxiliary motors, means energizing one of said auxiliary motors in accordance with the energization of the primary winding of said asynchronous motor, means energizing the other of said auxiliary motors from the secondary circuit of said asynchronous motor, differential means driven by said auxiliary motors for selectively moving saidcooperating contacts into and out of said range of vibratory movement in predetermined sequence in accordance with variations in the speed of said asynchronous motor, whereby selective intermittent engagement of said contacts is provided, and means controlled by the selective engagement and disengagement of said contacts for varying the speed oi said asynchronous motor.

8. Speed control means for an induction motor having a wound rotor, comprising a plurality of contacts, means for imparting to said contacts a vibratory movement, a plurality of individually movable cooperating contacts respectively associatei with said vibratory contacts and normably positioned beyond the range of vibration thereof, an auxiliary motor energizable from the primary circuit oi' said induction motor for rotation at a constant speed, a second auxiliary motor energizable from the secondary circuit of 40 diierential means driven by said auxiliary motors for selectively moving said cooperating contacts into and out oi' said range of vibration in predetermined sequence in accordance with variations in the speed of said induction motor to provide selective intermittent engagement of said contacts, the duration ci' contact engagement during each vibration depending upon the respective positions oi said cooperating contacts, each oi said cooperating contacts at one limit of movement providing continuous engagement with the associated vibratory contact, and means controlled by said contacts for selectively' varying the secondary resistance o! said induction motor to maintain a substantially constant speed.

9. Diiierential control means comprising a dii'- ierential mechanism including a member movable in accordance with variations in a condition to be controlled, a pluralityot contacts, means for imparting to said contacts a vibratory movement,

a plurality o! individually movable cooperating.

contacts normally positioned beyond said range said induction motor'for rotation at a speed cor-` responding to the speed of said induction motor,`

of vibration, a plurality of cams driven by said differential member for selectively moving said cooperating contacts into and out of said range of vibration yto provide intermittent engagementof said contacts, the duration of contact engagement during each vibration depending upon the respective positions oi. said cooperating contacts, each of said cooperating contacts being moved by its associated cam to a position providing continuous engagement with its associated vibratory contact before the next cooperating contact is moved into the range of vibration, and means controlled by said contacts for varying said condition to be controlled.

10. Differential control means comprising a differential mechanism including a housing movable in accordance with variations in a condition to be controlled, a plurality of contacts pivotally mounted adjacent said housing, means forA duration of contact engagement during each vibration depending upon the positions to which. said cooperatingcontacts are moved, and means controlled by the selective engagement and disengagement oi said contacts 4for varying said condition to be controlled.

11. Differential control means comprising a differential mechanism including a housing mov- Vable in accordance with variations in a condition to be controlled, a plurality of contacts piyotally mounted adjacent said housing, means 'fr imparting to said contacts a vibratory movement, a plurality of individually movable cooperating contactsrespectively associated with said vibratory contacts and normally positioned beyond the range of vibration, a plurality of annular cams secured to said housing for selectively-moving said cooperating contacts into and out of said range of vibration in accordance with the movement of said housing to provide intermittent engagement of said contacts, the duration of contact engagement during each vibration depending upon the positions to which said cooperating contacts are moved, said cams being arranged to move each of said cooperating contacts to a position providing continuous contact eny gagement before the next cooperating contact is moved into said range of vibration, means for adjusting said cams on said housing to vary the sequential movement of said cooperating contacts, and means controlled by the selective engagement and disengagement of said contacts fo varying said condition to be controlled. i

BENJAMIN W. JONES. 

